The present invention relates to an image forming apparatus for forming an image on paper and outputting the same, particularly to a paper ejection control for ejection to a stacking section.
Some of the image forming apparatuses for forming an image on paper in a printer, copying machine and printer, and for outputting it are provided with a stacker for loading a large amount of output paper with an image formed thereon. The stacker proper incorporates a stacking section equipped with an elevation function for elevating the stacked surface in response to the amount of loading. It has a capacity of loading, for example, 5,000 sheets of the paper with an image formed thereon.
Incidentally, in shortrun printing industry, post-processing of binding by drilling and stitching is performed by an offline post-processor 504, as shown in FIG. 8, in order to increase the operation efficiency. For example, when the image forming apparatus 501 is requested to execute a job of creating 100 copies of printed matter, each copy made up of 30 sheets, 3,000 sheets are loaded on the stacker 502 as a result. The loaded paper is taken out from the stacker 502 for each stacking section 503 and is carried to the offline post-processor 504, where a booklet is produced.
[Patent Document 1]
Official Gazette of Japanese Patent Tokkaihei 9-278271
Two jobs can be together subjected to post-processing; however, no mention is made of the problem that may be caused when various sheets of recording paper having been recorded in a plurality of jobs are present on the stacking section.
As shown in FIG. 8, when paper loaded on the stacker is bound in a book form by an online processor, only the paper related to one job for book binding has to be loaded on the stacking section. In an image forming apparatus wherein the next job can be registered by reservation during the output of the previous job, however, there is already no operation in many cases where the output of the reserved job has started upon termination of the previous job, with the result that the paper of the reserved job is often loaded on the paper of the previous job, according to the prior art. If paper has been loaded in this manner, the operator is required to sort out the paper related to a different job, before paper is fed to the offline post-processor. This has required much trouble and time.
In the meantime, a large number of small jobs where each job consists of 1 page or a few pages are executed continuously, and the outputs of these jobs are loaded collectively. Such a configuration of data-center form is also practiced. For example, as shown in FIG. 9, when a great number of direct mail documents having the same text and different addresses are to be printed, one job corresponds to one address. After image formation, the printed matter is put into envelopes by the offline post-processor or manually. Thus, the capability of ejecting the outputs of many jobs, one on top of another, into one and the same stacking section is essential to ensure a high level of work efficiency.